Joe Caliro fears there will come a day when people forget about the Negro Leagues, so the Portsmouth, N.H., resident is doing what he can to keep it fresh in our memories.

Caliro, 80, will present an exhibition and lecture called “The History of the Negro Leagues’’ from 11 a.m. to 2 p.m. Wednesday at the Portland Public Library. The lecture will be held from noon to 1 p.m. in the Rines Auditorium, with viewing of the collection before and after.

The exhibit, free to the public, will include more than 400 memorabilia items Caliro collected over the years, including 51 autographed baseballs.

“I feel this is an important part of American history,’’ said Caliro, who has presented similar events at several libraries in New Hampshire. “I was in the military for 26 years and I have a strong sense this is a part of American history that a lot of people don’t understand and don’t know about. I know it seems to me that there are a lot of people who are shocked when I tell some of my stories.’’

The Negro Leagues were the only option for black pro baseball players for several decades until Jackie Robinson broke the color barrier in 1947. The first Negro League started in 1920. The last major league season was 1951. Some Negro League clubs continued as minor league teams for several years.

Caliro’s lecture will include stories of barnstorming Negro League teams that played in Maine, including one Massachusetts team that featured pitcher Bill “Cannonball’’ Jackman. Caliro said Jackman was paid $10 per strikeout and $100 per game pitched.

“There were definitely ties to New England, ties to Maine,’’ said Caliro. “You had Negro League teams playing in Sanford and in Pettingill Park (in Auburn). There is a lot of history that ties the Negro Leagues to New England.’’

Caliro’s interest in the Negro Leagues began while he was in the military, serving in Biloxi, Miss. He was asked by his superior officer “to prepare a class on racial relations, to acclimate the military personnel on life in Mississippi as it was in 1956.’’

After presenting the details of his class, Caliro said it was canceled. “As one officer told me, the more you stir things, the worse it gets.’’

But while preparing for the class, Caliro studied the tribulations of Robinson and his wife, Rachel, as they traveled the South. He became a student of the Negro Leagues, collecting memorabilia wherever he could. Among his autographed baseballs are some signed by Willie Mays, Hank Aaron, Ernie Banks, Leon Day, Monte Irvin, Larry Doby, Buck Leonard, Ray Dandridge and James “Cool Papa’’ Bell – all enshrined in the National Baseball Hall of Fame in Cooperstown, N.Y.

Mike Lowe can be contacted at 791-6422 or at mlowe@pressherald.com

Twitter: MikeLowePPH